Calendar of Physics Talks Vienna

Quantum Metrology with Bose Einstein Condensates

Speaker:

Markus Oberthaler (Kirchhoff Institute for Physics, University of Heidelberg)

Abstract:

One aspect of metrology, the science of measurement, is the exploration of the ultimate precision limit.
It is known for quite some time that the new possibilities in quantum mechanics allow the surpassing of
the ultimate classical precision limit given by counting statistics. Quantum metrology is about the
exploration of these new limits. The goal is the generation and characterization of useful quantum mechanical resources
for going beyond the classical precision limits. Since the gain in precision is intimately connected to quantum
entanglement in many particle systems these investigations are also interesting from the fundamental point of view.
In the colloquium I will discuss in detail how Bose Einstein condensates can be used to generate entangled
many particle states which push atom interferometry beyond the classical limits. I will use the system of two
component atomic condensates as a model system for explaining how quantum correlations arise and how
they can be used for improved estimation of a phase shift in an atom interferometer. The simplest form of
useful many particle quantum states are spin squeezed states which can be classified as Gaussian states.
I will also report on the latest results revealing that Bose Einstein condensates make it possible to generate
deterministically non-gaussian states. The experimental extraction of a bound of the quantum
Fisher information implies that these states also surpass the classical limits of the phase estimation precision.

Date:

Mon, 19.01.2015

Time:

17:00

Duration:

90 min

Location:

Lise-Meitner Lecture Hall, 1st floor; Strudelhofgasse 4, 1090 Vienna

Contact:

J. Schmied

Lck cluster dynamics in live cells

Speaker:

PhD Florian Baumgart (TU Wien, IAP)

Abstract:

During the instigation of an adaptive immune response, TCR-pMHC (T cell receptor- peptide major histocompatibility complex) binding results in the phosphorylation of intracellular tyrosine residues on the ζ-chains of the TCR, recruitment of adapter molecules and downstream signaling. Initial TCR phosphorylation is primarily carried out by lymphocyte specific kinase (Lck) making it a key molecule for T-cell signaling. Lck has been shown to form nano-scale clusters that can be visualized by super-resolution microscopy techniques. However, neither the molecular determinants nor the function of Lck clustering are clearly understood.
We carried out single molecule microscopy of fluorescent protein-tagged Lck expressed in JCaM1.6 cells to elucidate the mechanisms that lead to Lck clustering in the plasma membrane. Our single molecule tracking data show transient immobilization of Lck molecules

Precise beta decay measurements require the inclusion of radiative corrections for their analyses. During the beta decay process also a bremsstrahlung photon can be emitted. Due to the low energy of this photon, the photon bremsstrahlung part of the radiative correction can be reliably calculated (it is independent of strong interaction effects). Accordingly, the radiative neutron decay experiments do not give any information about strong interaction dynamics.
The photon bremsstrahlung changes the kinematics of the beta decay process, and this is important for the experimental analyses.
The computations are technically complicated, they require more-dimensional integrations. It is difficult to compute these integrals analytically, but it is more easy by Monte Carlo methods. The virtual radiative corrections have infrared and UV divergences, and they depend also on non-perturbative strong

Neutrino oscillation experiments determine very precisely the neutrino mass square differences, but they are insensitive to the absolute neutrino mass scale.
Indirect neutrino mass determinations, like neutrinoless double beta decay or cosmology, are model dependent.
The aim of the KArlsruhe TRItium Neutrino experiment KATRIN is the direct and model independent determination of the absolute neutrino mass scale down to 0.2 eV. For this purpose, the integral electron energy spectrum will be measured close to the endpoint of molecular tritium beta decay. The electrostatic retardation method with magnetic adiabatic collimation (MAC-E filter) combines high energy resolution with high statistics and small background. The various components of the experiment (gaseous tritium source, pumping-transport system, pre- and main spectrometer, detector and rear system) will be reviewed, together with

Date:

Thu, 22.01.2015

Time:

16:30

Duration:

60 min

Location:

Atominstitut, Stadionallee 2, Wien 2, Seminarraum

Contact:

H. Abele

Searching for dark matter in the gamma-ray sky

Speaker:

Alejandro Ibarra (Technical University Munich)

Abstract:

The search for the gamma-rays which are presumably produced in dark matter annihilations is hindered by the existence of large, and still poorly understood, astrophysical backgrounds. In this talk we will review various approaches to search for dark matter in gamma-rays and we will emphasize the importance of sharp spectral features for the identification of a dark matter signal. We will review the status of the search of the various spectral features that arise in Particle Physics scenarios and we will discuss the interplay with other search strategies.

Date:

Fri, 23.01.2015

Time:

10:30

Duration:

60 min

Location:

Seminar Room, Wohllebengasse 12-14 (Academy building), ground floor

Contact:

Josef Pradler

Precision measurements in beta decays

Speaker:

Martín González-Alonso (Lyon Institute of Origins)

Abstract:

Precision measurements in nuclear and neutron beta decay offer a sensitive window to search for New Physics. The bounds obtained from these experiments will be reviewed and compared with current LHC searches in a model-independent way. I will also discuss the relevant hadronic form factors and the connection with the nucleon mass splitting.